Answer
A non-linear load-deflection curve in a theoretical linear wave spring (Crest-to-Crest) often points to 'Wave Nesting' or 'Radial Binding'. If the waves are not perfectly aligned, they may start to nest into one another as they flatten, changing the effective number of active turns $n$. Alternatively, if the spring is expanding and hitting the bore wall (Radial Binding), the friction against the wall adds an artificial load. Another possibility is 'End-Turn Interference', where the transition from the flat end-turn to the first wave is too abrupt. Troubleshooting requires a load-deflection test with a plot. A sudden increase in slope ($K$) suggests binding or solid height contact, while a decrease might suggest localized yielding. Precision grinding of the ends and ensuring proper bore clearance are the standard fixes.
